Flowback data analysis has been recently considered by the industry to quantify hydraulic fracture parameters such as, effective fracture pore-volume. Tools based on simulation and rate transient analysis have been applied for flowback analysis. However, too many unknown parameters, together with complex production mechanisms lead to uncertain and non-unique results. This paper illustrates how flowback data can be interpreted to estimate effective fracture pore-volume and its relationship to fracture design parameters.
This study starts by addressing some limitations of the previous flowback models. In particular, the effects of water expansion and fracture closure are included in the proposed model. The resulting linear relationship is applied to flowback data from eight tight oil and gas wells in Anadarko Basin to estimate effective fracture pore-volume. The estimated effective fracture pore-volumes are compared with fracture design parameters such as total injected volume of water, soaking time, gross perforated interval, and proppant concentration.
The results indicate that fracture closure is the main mechanism for single-phase water flowback. Therefore, effective fracture pore-volume largely depends on fracture compressibility. The results also show that soaking time, gross perforated index, and proppant concentration are among the key design parameters for an optimum fracturing treatment.